Thrust 1: Explosives Characterization, Aging of Explosives and Viability and Sensitivity Over Time

At present there is little information on the impact sensitivity of nanoscale energetic materials at various temperatures. By far the majority of small scale experiments have been conducted at room temperature. Interrogating the effects of temperature on the sensitivity of explosives is most often performed ex-situ where the explosive is artificially aged at a given temperature and then tested at room temp. As such, there are critical open questions regarding the aging of explosives, their viability and sensitivity over time, and their response to different thermal environments. The proposed research will answer critical basic science questions that will lead to improved understanding of the performance of energetic materials.

Drop-weights are fitted with monitoring systems to allow stress-time characteristics of the impact to be measured. Currently an instrument is available at Texas Tech which will allow for drop-weight tests to be conducted at temperatures ranging from ambient to 300 degrees Celsius.

This project is suitable for an undergraduate since publishable results can be obtained over a 10 week period and the sample size of the explosive (~10 mg) has no significant handling issues. An undergraduate student worked on the development of the apparatus in 2008-2009 academic year and a publication is under review. The project is an ideal outreach tool since students are excited about the use of high explosives and they often perform demonstrations with this apparatus for secondary school students visiting Texas Tech.

Thrust 2: Standoff Radar Detection of Concealed Body-Worn Explosives

It is tremendously important to detect dangerous concealed targets at a safe distance. Suicide bombers pose an increasingly critical terrorist threat due to their free mobility and ease of concealment. There are many ways to detect explosives on individuals with intimately close sensors — such as airport security portals — but identifying threats at 50 meters is much harder. Radar is one of the very few means of sensing dangerous objects obscured by clothing half a football field away. Signals will bounce off the shrapnel-generating metal explosive casings, so they should be effective in detecting pipe bombs. The problem is that skin and muscle tissue contain a great deal of water, so humans reflect radar almost as well as metal. Even innocent individuals show up as strong signals.

Our research group at Northeastern has been working on ways to improve explosive-detecting radar with improved antenna design and signal processing algorithms to measure the “lumpiness” of the skin surface. If there are abrupt height changes on the skin, there might be a pipe strapped to it. These abrupt changes are what we are looking for, and radar can pick them out, even at a safe distance.

REU students would help with the computer simulation of radar and electromagnetic field modeling to predict the details of how the waves bounce around when they interact with characteristic threat geometries.

Underground tunnels present both military and homeland security threats since smugglers use them as transit routes for trafficking weapons, explosives, people, drugs, and other illicit materials. Detecting and imaging the presence of tunnels in any given region of ground is possible because the air that fills them is materially quite different from anything else underground. The Spotlight Synthetic Aperture Radar (SL-SAR) has been used due to its ability to scan large areas of terrain in a short amount of time, which is ideal for tunnel detection. In order to obtain strong and distinct target signals, Underground Focusing, based on ray refraction at the ground surface is being considered. This presents a challenge since the technique requires an estimation of the ground characteristics, and the random roughness of the soil surface tends to distort the reconstructed image of the analyzed geometry.

This project will explore the impact of the ground surface roughness in Underground Focusing SAR imaging for tunnel detection applications. The study will be computational, simulating incident plane wave interactions with the ground with and without tunnels. Shallow tunnels in dry soil can be easily imaged. We continue to explore ways of imaging the deep tunnels targets in moist clay.

The Advanced Imaging Technology project began Fall, 2010 with the goal of developing an improved multi-modality portal-based passenger screening system. Millimeter-wave, x-ray backscatter, infrared sensing, and Terahertz sensing are being considered. Initial concentration in mm-wave imaging makes use of optimal antenna placement, model-based inversion, superior frequency specification, and custom designed radar hardware. A specially-built hardware platform has been designed and built. Consisting of mechanical and electrical subcomponents it will facilitate reconfigurable sensor placement in order to develop a multi-static imaging radar system.

This project will work on improving the radar hardware, computer modeling, image reconstruction algorithms and/or collection of experimental data for concealed object detection.

The objective of the proposed work is to extend the existing technology of Remote Raman Spectroscopy (RRS) toward the application of explosives detection in range (greater than 100 meters), in detection limits and in terms of detection of Raman signatures of realistic explosives-related materials as they pertain to the detection of Improvised Explosive Devices (IED). The applications of this technology in the persistent problem of IED detection and defeat and in vehicle bomb confirmation by detecting traces of active explosives, formulations and degradation products via the methodologies to be developed are at the very heart of the proposed tasks.

This project addresses advancing the instrumentation by designing optimized versions of visible (VIS) and near infrared (NIR) Raman Telescopes. It also focuses on the issue of selectivity and other issues that can be used for prediction of spectral signals (signatures and sensitivity) of environmentally exposed explosives and real world explosives and devices containing explosives, such as IEDs.

This will give a better understanding of the chemical signatures from exposed explosives and the ability to predict the performance of spectroscopic measurement techniques for measuring many different types of explosive materials.

There are several projects under the umbrella of nanotechnology based Raman sensing of threat compounds. Students from several fields are welcome: Chemistry, Biology, Physics, Chemical and Electrical Engineering.

Nanostructures made of noble metals: Ag, Au and Cu in their zero valence state are used to augment Raman signal of analytes adsorbed or in very close proximity to the metallic nanostructures. Spheres, cubes, rods, prisms and irregular and non-periodic forms present in colloidal or condensed forms are tailor made to achieve particular forms or structural characteristics. The focus of the research is on the optimization of the synthesis of the metallic nanostructures for use in Surface Enhanced Raman Scattering (SERS) applications.

SERS is a powerful technique which combines extremely high sensitivity, due to enhanced Raman cross-sections, comparable or even better than fluorescence emission, with the observation of vibrational spectra of adsorbed species, providing one of the most incisive analytical methods for chemical and biochemical detection and analysis at very low concentrations of analyte. Target analytes are high explosives, chemical and biological threat agents or their simulants, toxic industrial compounds, pesticides and other environmental pollutants and biochemical compounds.

There are several projects under the umbrella of nanotechnology based Raman sensing of threat compounds. Students from several fields are welcome: Chemistry, Biology, Physics, Chemical and Electrical Engineering.

A research project to pursue studies in applications of mid-infrared (MIR) Quantum Cascade Lasers (QCL) for the remote detection of highly energetic materials (HEM) and biological threats that could be used as Weapons of Mass Destruction is currently ongoing at the ALERT Research Lab at UPRM. MIR laser-based excitation sources with recently developed wide-range scanning capabilities will be applied to a wide range of chemical and biological threats in remote detection mode to establish the next generation of standoff sensors for defense and security applications. The proposed work entails the modification of commercial systems to increase remote distance detection capabilities, testing for detection of threat chemical and biological threats (CBT) on substrates and in vapor phase and development of algorithms for discrimination of analytes in complex mixtures and in the presence of interfering background.

Target chemicals will include high explosives (RDX, PETN, TNT, HMX, Tetryl), homemade explosives (TATP, HMTD, TMDD, ammonium nitrate urea nitrate), mixtures (Pentolite, ANFO), formulations (C4, SEMTEX-H) and biological agent simulants (Escherichia coli, Bacillus thuringiensis, Bacillus subtilis, Bacillus cereus, Staphylococcus aureus, Staphylococcus epidermidis, Salmonella Tennessee, Klebsiella pneumoniae). Spectroscopic signatures of the CBT agents will be measured, and a library will be built to be used in standoff detection/identification experiments. Quantification/discrimination studies as well as the effects of substrates, matrices and interferences on identification and quantification will also be investigated.

A novel, laser mediated method of desorption/detachment which augments the vapor concentration of non-volatile compounds in the form of a plume is proposed for enhanced detection of threat agents using optical spectroscopy. In particular, telescope based Raman Spectroscopy Chemical Point Detector and telescope based Fourier Transform Infrared Spectroscopy will be used to examine the surface and vapor emitted, respectively, of substrates containing trace amounts of target threat compounds that can be used as Weapons of Mass Destruction. Among the target threat chemicals are nitroaromatic/nitroaliphatic explosives (TNT, RDX, PETN), mixtures (Pentolyte) and formulations (C4/Semtex); Chemical Warfare Agents Simulants and Toxic Industrial Compounds. Fundamental and applied studies of desorption/laser photodetachment scheme proposed will be conducted. Effect of interferences, including photodegradation products will also be characterized. Active Chemical point detection based on Raman scattering will be used in pulsed mode from the near infrared (785 nm) to the deep ultraviolet region (266 nm). Since photodesorbed species are assumed to be vibrationally excited, FTIR detection will be used in passive, wide area mode. Quantification/discrimination studies as well as sensor fusion experiments will also be carried out.

Making a real difference

Students participating in the REU program work on government and industry sponsored projects. Many see their work put to use in the field.